Power vehicle with hydrostatic power transmission to motive and operating drives



sept. 24, 1963 M. Home 3,104,528

POWER VEHICLE WITH I-IYDROSTATICA POWER TRANSMISSION TO MOTIVE AND OPERATING DRIVES Filed Sept. 1. 1960 ATTORNEY' United States Patent O 3,ll)4,528 v PWER VJHCLE WlTll HYDRGST'HC PWER TRANSMISSN T0 MTlVE AND UPETENG DRH/ES Martin Hrig, Aschaenhurg, Germany, assigner to Gesellschaft tur Lindes llismaschinen Aktiengesellschaft, Holiriegelslrreuth, near Munich, Germany, a company oi Germany Filed Sept. l, 1964i, Ser. No. 66,371 Claims priority, application Germany Sept. S, 1959 3 Claims. (tCl. oil- 52) This invention relates to the wheeled vehicle art, and is concerned with improvei. ents in hydrostatic power transmission to the motive and op-erating drives of such vehicles.

Tractors and implement-carriers are known, especially in agriculture, in which an internal combustion engine drives two pumps or la hydrostatic power transmission, one of which pumps advances a hydrostatic motor for the motive drive, while the other pump feeds hydrostatic motors for the operation of working implements. These vehicles are usually so equipped that either a (motive) motor acts directly on the drive wheels of the vehicle or one motor drives the drive wheels directly while Ia conversion drive for changing the torque land rpm. between motor and drive wheel lies within the frame of the direct drive. The operation or auxiliary drive can logically be driven by a hydraulic motor, which is ted by the other pump, through various mechanical gear connections, or several hydraulic motors and cylinders are provided which can be connected at will into the hydraulic power flow, through ya hydraulic control device. Usually in the cases of agricultural vehicles, the drive for working equipment is needed only within a lower speed range of the vehicle, while in higher speed ranges a drive for implements lis no longer provided.

Therefore it has been suggested that the gross output for the upper speed ranges or the vehicle be supplied both by the pump ot the motive drive and additionally by the other pump. ln principle, it is the same in the present problem if, instead of one hydrostatic pump and one hydrostatic motor, two or more are provided.

The hydrostatic pumps suitable for this purpose have a wide range of output, which can be regulated, preferably continuously (step-less), from a minimum to a maximum amount, of which the minimum may be zero or the maximum amount may be delivered in both directions, so that the drive is reversible. The variation of the output of these pumps is attained by mechanical means. The adjustment of this mechanical means requires `a certain, directed power eiect. As a rule, the adjustment-effecting force increases with the output, while in the zero position no power etlect is necessary. The force for the `adjustment of the output is, opposed by the reaction or return forces fromY` the hydraulic side of the pump, of which the magnitude usually increases with the hydraulic pressure.

Since the hydrostatic pressure in the hydraulic system usually depends on the amounts of mechanical resistance in the drive and could, with increasing resistance, become greater than allowable, over-pressure or safety valves are built in by which the excess output can escape, so that the hydraulic pressure cannot exceed a certain, preferably adjustable, maximum pressure. This arrangement may, according to its purpose and its design, involve great losses, since the energy to be applied is proportional to the amount and pressure of the output, while the energy utilized corresponds only to the output absorbed and its pressure. This is true, for example, in units which lift a load within a certain time and :then must hold it suspended. During the lifting an advancing ICC amount and pressure of feed, and thus `an `advancing capacity, is required, while during the holding in the suspension position, only a hydraulic pressure is necess-ary, the `advancing amount only having to compensate possible relaxation losses, and thus being very slight.

There are arrangements, however, in which the drive .resistance may vary between rather wide limits even during one operation process; thus, vtfor example, when during an operation process or program the applied moment of a load lies at variable effective lifting .arm lengths or if, for example, motive resistances `on a roadway of diilerent characteristics are to be overcome.

This invention relates to lsuch a power vehicle, especially for agriculture, construction :and industry, with hydrostatic power transmission to motive and operation gears, comprising at least two pumps and motors driven by `an internal combustion engine as power source, in which within lower vehicle speed ranges at least one pump can act on the motive drive or drives and at least one other on the operation drive, and in ythe upper speed ranges at least one ot the other pumps can additionally feed the motive drive or drives, with the distinction that the ladjusting :forces to be exerted (in the adjustment of the output of at least one of the pumps which can act, through at least one control element, on the operating and motive drives) can be elastically retarded. The adjusting force acting mechanic-ally on at least one of the pumps for the operation drive should, accordingly, be elastically retardable, for example, be overcome by reaction or return forces, so that the output is diminished in accordance with `the withdrawal. These forces should,

however, `also ret-urn to the original output setting with a :lessening of the reaction or return forces. T, for example, two or more operation gears or different characteristics lare driven by one pump and one control element is used to select 4the .gears to be set in operation, then it is advisable for the adjustment forces to be adjustable (variably set) by the control element, according to the desired output wanted. in this way, the amount and pressure of feed ideally given to the drive are predetermined and can'be reduced on exceeding certain values. Since the control device can be set on the various drives, it is advisable that the variable setting of the adjusting forces be undertaken in combination with the adjustment of this cont-rol device, vfor example, 4by a simple mechanical connection. Rather than depend exclusively on :the effect of reaction or return lforces, which occur through the type of construction, it is advisable to provide a counter-force device which can partly or wholly 'cut oit the output at a maximum pressure exceeding that prescribed for the drive in question, which may over-come the force of the feed setting. This counter-force device, which may, for example, consist of Ia hydraulic cylinder with appropriate transmission :to the pump, can likewise tbe adjusted to advantage, in combination with the control device. This connection may be of a purely mechanical sort or be of the hydraulic sort. For maintaining great efficiency it is advantageous if the responsive pressure of the counterforce device lies below the overload level of the safety valve or valves. Especially rgood relations are achieved when the combined faction of power setting device and counte -force device-can be set -at :a :feed amount automatically not exceeding a certain pressure with variable workloads and thus using the best capacity of the internal combustion engine. To utilize fully the y.advantages of variable setting vand counter-force devices and thus to be able t0 equip the power vehicle with the drives of greatest capacity, it is advantageous-and even in cases of temporary overstrain thoroughly profitable-that the sum of the maximum capacity of the pumps be greater than the maximum capacity of the energy source. In

the working .together of the one pump or pumps, it is advantageous if the cooperation of the setting force device and the counter-force device can be adjusted independ- .ently of the response of a `capacity regulation on the first .pump or pumps.

This invention will be further described, with reference to the accompanying drawing, in which the single FIG- URE is a diagrammatic representation of `an organization embodying the principles of the present invention.

The drawing shows in diagram ian example of the design or use of the subject of this invention on a tractor or implement carrier, especially Vfor agriculture. By means :of an internal combustion engine l a hydraulic power transmission is activated through meshing gears 2 and 3 for the motive drive, which consists of a pump 4, a motor 5, two conduits 6 and 7 lying between pump 4 and motor 5, a bevel gear combination 8 and 9, a compensating gear lil, two semi-axles `ll and l2. and two drive Iwheels i3 and 14. The output of pump y4 Jis continuously regulated through lever l yfrom zero to max-inium values in both directions. "Ihre turning direction of drive wheels i3 and i4 is determined by the tilt of pump 4. A .diiferential lock lo can bind .the two axle halves 11 and l2 rigidly together. The tractor is equipped with a shaft 17 which can be driven, dependent on direction, `either by a coupling 18 `and gearing 19, 20 from the internal combustion engine l, or: by coupling 2l and gearing 22 and 23 of motor S, in the usual way.

With gear 2 .there is engaged, also, a further gear 24 by which latter a second pump 25 is driven. This pump 25 belongs to a second hydrostatic power transmission which leads through `conduits 26 and 27 to a reversing, changeover or switching element or device 28 and can be transmitted further to the various operating 'equipment as well as to hydrostatic power transmission for the motive drive.

As operated devices there are represented a power lever unit 29, a mowing ydevice 3d, which is connected through conduits 3l and 32 with the switching element 28, and cable lwinding drive 33, to which latter conduits 34- and 35 lead from the switching element 28. The switching element 28 is activated by lever 36. A lever 37 is used .to adjust the tilting of pump 2.5, thus regulating the output of the pump. An adjusting device according t0 this invention engages with pump 25, and consists of a can (cage) 38 with a point of application 39, a thrust rod 40 with a point of application 4l, which is connected with pump 25, a thrust rod 42 with :a point of application 43 and a spring 44 lying between the two thrust rods 4t) and y41?..

A counter-force device is also provided which consists of a hydraulic cylinder 45, a feed line 46 and a point of application 47. The line 46 is connected with pressure line 26 and the point of application 47 is so connected with the pump 2S that conversion can be adjusted, for example, -by varying the effective length of the lever.

To produce a How of power from the pump 2S to an operated device 29, 30, 33 the control element Z3' can be brought, by means lof the lever 36, into the proper position and the pump 25 brought to feed capacity by lever 37. It is better and simpler however, if by means ofthe lever 36 (through .a connection rod 4S', articulated, on the one hand, on lever 36 at point 35' and, on the other hand on fulcrum 39, with, if desired, possible variation of the point of application 43), the spring cal-ge 44 also, and perhaps the thrust rod 42 are so moved in the arrow direction 4S that the pump 25 is adjusted by the thrust rod 40 to the output wanted. Thus, the hydraulic power or energy transmission is effected by moving a lever.

The output of the pump 25 tlows through `the conduit 26 to the cable-winding drive `and from the drive returns through conduit 27 to the pump 25. Thus, in the conduit 25 a feed pressure prevails which is transmitted 4 through conduit 46 into the hydraulic cylinder 45, where a counter-force is produced.

As long as the feed pressure does not exceed the set operation pressure, the `counter-force cannot overcome the tension of spring 44, and the feed setting of pump 2S remains unchanged. However if, for one of the `usual reasons, the feed pressure exceeds the allowable set work-` ing pressure by a certain amountwhich may be adjusted-then the counter-force overcomes the tension of spring 44 and the lever 37 for the adjustment of the output is set back, -without changing the position of the cage 38, in such manner that the output is decreased,

so that in some of the usual cases the pressure is decreased to about the operation pressure. In the somewhat different case of an operation program, at lany rate, the overpressure is stopped until the pump feed goes to zero, that is, until lever 37 goes all the way back. Both these processes are carried out by the arrangement shown. Since under some circumstances of different drives, different yfeed amounts .at a different presusre are to be delivered by pump 25, the feed settings can best be varied f working pressures for the different purposes in a powerl lifting unit 29, for example. if this power lift is used for the rather rapid lifting of operation implements, then a high working pressure is needed and in each case a certain feed amount according to the total transmission. In this case, therefore, the lever 37 with activation of lever 36 for the control element 28 can vary the pump 25 greatly; at the same time, however, the original tension of the spring 44 inside the cage 33 which is moved` quite far in the arrow direction 43, must be correspondingly great. In the upper end position of the power lifter,

the feed amount must be turned of; this takes place through the overpressure which builds up in the end position and sets back the pump 25 to act on the counterforce device. lf, however, the power lifting unit is applied, in

a conventional way, as a wheel pressure reinforcement f of the drive wheels, it is only necessary to shift the weight of the implement partially on the power lifter and so on the hind axle, so that in this case the power lifter is only set in action -with lower pressures with, in some cases, a very slight deflection. This is attained by another setting of the lever 36 on the control element 28, or by maintaining the setting of lever 36 and changing the position of the cage 38 and the original tension of spring 44 by a relative withdrawal of thrust rod 42 in suitable fashion. As long as this new setting is maintained, the wheel pressure reinforcement is effective.

4In another case for example, in mowing machine drive 30, there may be a limiting or blocking of the mowing bar by a foreign body, which also leads to an increase of pressure in conduit 26, which acts on the counter-force device and in the combined action, already described, with the setting force device, the feed of the pump is shut olf so that there results protection against a breaking of vthe mowing device or its gear. At another settingY of the and the counter-force device, a continuous (step-less)` speed regulation in this range is dependent on the motive resistance, so that the highest possible utilization of the capacity of the-internal combustion engine is attainable.

lf the safety valves in the various power transmissions are set above the pressure which is necessary to let the counter-force device overcome the setting force device, these will normally never have to respond, and incidental losses in capacity will not occur. Quite generally, the arrangement according to this invention allows the highest possible utilization of the internal combustion power engine at an ideal eiiciency.

The arrangement presented can be used to advantage also on working machines and vehicles with hydraulic power transmission devices, as used for example in construction work and in industry.

l claim: v

1. Hydrostatic transmission for a vehicle with at least one secondary drive such as an apparatus carrier or a tractor with a pivot shaft, the transmission including a rst pump and a second pump and at least two motors operatively connected with said two pumps, one motor being a main driving motor, which motors are connected with each other through pipe lines, both of said two pumps being driven by an internal combustion engine and said first pump being connected by one ofksaid pipe lines with the main driving motor, a switching element being provided in the pipe line by which the second pump can be connected with the main driving motor or with another motor, characterized in that said second pump (2S) which can be connected either with the main driving motor (5) or with another motor (33) is provided with a control element (37 to 47) for varying the operation of said second pump (25) in dependence on the pressure obtaining in said pipe lines (26, 27) in such a way that when a predetermined maximum pressure is exceeded said second pump (2,5) is regulated to a lower delivery rate, said hydrostatic transmission being further characterized in that dierent driving devices (30, 33) arbitrarily can be connected, by means of said switching element, with the regulatable second pump (25) provided with the control element (37 to 47), and wherein a lever (36) etrecting reversal of the switching element (28) is connected with the adjusting device (39) of the control element (37 to 47).

2. Hydrostatic transmission for a vehicle with at least one secondary drive such as an apparatus carrier or a 6 tractor with a pivot shaft, the transmission including a first pump and a second pump and at least two motors operatively connected with said two pumps, one motor being a main driving motor, which motors are connected f with each other through pipe lines, both ot said two pumps being driven by an internal combustion engine and said lirst pump being connected by one of said pipe lines with the main driving motor, a switching element being provided in the pipe line by which the second pump can be connected with the main driving motor or with another motor, characterized in that said second pump (25) which can be connected either with the main driving motor (5) or with another motor (33) is provided with a control element (317 to 47) for varying the operation of said second pump (25) in dependence on the pressure obtaining in said pipe lines (26, 27) in such a way that when a predetermined maximum pressure is exceeded said second pump (25) is regulated to a lower delivery rate, in which hydrostatic transmission the control device consists of an adjusting lever (37), a cylinder (45), and a piston sliding in said cylinder (d5) said cylinder being connected with the said pipe line (26) of said second pump (25), and a spring (44), -said piston being connected with a connecting rod which can be articulated by means of aslide bar (47) at any point of the crank that the spring (44) engages the adjusting lever (37) and in which the initial stress of the spring (44) is adjustable.

3. Transmission according to claim 1, in which the main driving motor is fed by said first pump and constitutes the driving element connected to said' second pump, and in which the volumetric capacity of the main driving motor is such as to accept whatever liquid volume is supplied to it by said second pump.

References Cited in the file of this patent UNITED STATES PATENTS 2,103,530 Henry Dec. 28, 1937 2,238,060 `Kendrick Apr. 15, 1941 2,745,253 Towler et al May 15, 1956 2,955,917 Roberts et al. Oct. 11, 1960 FOREIGN PATENTS 412,816 Germany Mar. 23, 1922 

1. HYDROSTATIC TRANSMISSION FOR A VEHICLE WITH AT LEAST ONE SECONDARY DRIVE SUCH AS AN APPARATUS CARRIER OR A TRACTOR WITH A PIVOT SHAFT, THE TRANSMISSION INCLUDING A FIRST PUMP AND A SECOND PUMP AND AT LEAST TWO MOTORS OPERATIVELY CONNECTED WITH SAID TWO PUMPS, ONE MOTOR BEING A MAIN DRIVING MOTOR, WHICH MOTORS ARE CONNECTED WITH EACH OTHER THROUGH PIPE LINES, BOTH OF SAID TWO PUMPS BEING DRIVEN BY AN INTERNAL COMBUSTION ENGINE AND SAID FIRST PUMP BEING CONNECTED BY ONE OF SAID PIPE LINES WITH THE MAIN DRIVING MOTOR, A SWITCHING ELEMENT BEING PROVIDED IN THE PIPE LINE BY WHICH THE SECOND PUMP CAN BE CONNECTED WITH THE MAIN DRIVING MOTOR OR WITH ANOTHER MOTOR, CHARACTERIZED IN THAT SAID SECOND PUMP (25) WHICH CAN BE CONNECTED EITHER WITH THE MAIN DRIVING MOTOR (5) OR WITH ANOTHER MOTOR (33) IS PROVIDED WITH A CONTROL ELEMENT (37 TO 47) FOR VARYING THE OPERATION OF SAID SECOND PUMP (25) IN DEPENDENCE ON THE PRESSURE OBTAINING IN SAID PIPE LINES (26, 27) IN SUCH A WAY THAT WHEN A PREDETERMINED MAXIMUM PRESSURE IS EXCEEDED SAID SECOND PUMP (25) IS REGULATED TO A LOWER DELIVERY RATE, SAID HYDROSTATIC TRANSMISSION BEING FURTHER CHARACTERIZED IN THAT DIFFERENT DRIVING DEVICES (30, 33) ARBITRARILY CAN BE CONNECTED, BY MEANS OF SAID SWITCHING ELEMENT, WITH THE REGULATABLE SECOND PUMP (25) PROVIDED WITH THE CONTROL ELEMENT (37 TO 47), AND WHEREIN A LEVER (36) EFFECTING REVERSAL OF THE SWITCHING ELEMENT (28) IS CONNECTED WITH THE ADJUSTING DEVICE (39) OF THE CONTROL ELEMENT (37 TO 47). 